Many existing techniques for multiband image fusion are based on component substitution [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, multiresolution analysis [8]}, [9]}, [10]}, [11]} or spectral unmixing [12]}, [13]}.
More recent model-based variational methods have been shown to yield state-of-the-art results [14]}, [15]}, [11]}, [7]}. The standard image-formation model used in these works is
\(\mathbf {Y}_\ell = \mathbf {S}\mathbf {B}\mathbf {Z}+ \mathbf {N}_\ell \quad \text{and} \quad \mathbf {Y}_h = \mathbf {Z}\mathbf {R}+ \mathbf {N}_h,\) 
